This invention relates to the art of tools and, more particularly, to an improved mechanism for supporting a woodworking tool beneath a work supporting surface for adjustment of the position of the tool bit or cutter relative to the work supporting surface.
The present invention finds particular utility in connection with the support of a fixed base router relative to a work supporting surface and, accordingly, will be illustrated and described in detail herein in connection with such a router. At the same time, however, it will be appreciated that the invention is applicable to the support of other tools of the character wherein a driven bit, cutter, blade, or the like is supported for vertical adjustment relative to a work supporting surface such as a workbench or table.
It is known, as shown for example in Canadian patent application 2,314,653 in the name of Darrin E. Smith to support a fixed base router beneath a work supporting surface such that the router and thus a router bit to be driven thereby is vertically adjustable relative to the work supporting surface. The adjustability provides for accommodating a wide variety of router bit profiles and, as is well known, such routers are used by woodworkers in connection with the production of furniture, decorative moldings, picture framing strips, and, in connection with the joining of wood pieces, the forming of dovetail joints, box joints and the like. High quality work in connection with the use of routers for the latter and other purposes requires not only a good router, sharp bits, good wood, and a skilled operator but also, precision with respect to obtaining and maintaining a truly perpendicular orientation of the router axis and thus the router bit axis with the plane of the work supporting surface. Further, high quality work requires stability against vibration during a cutting operation, and the ability to accurately and minutely control adjustment of the vertical position of the router bit relative to the work supporting surface.
The desired vertical orientation between the router bit axis and work supporting surface is affected by such factors as the degree of precision in machining the component parts of the router support mechanism and/or the manner in which the router is supported relative to the work supporting surface. With regard to the latter in particular, obtaining and maintaining a precise vertical orientation between the router bit axis and the work supporting surface in the Darrin apparatus is difficult, at best, because the router and the router carriage are supported relative to the work supporting surface by a pair of posts which are laterally offset from the axis of the router and thus the router bit, whereby the router and carriage are supported in cantilever fashion relative to the work supporting surface. Accordingly, the weight of the router and carriage can result in skewing of the router bit axis relative to the desired vertical disposition thereof relative to the work supporting surface. Moreover, the cantilevered support of the router and carriage relative to the guide rods imposes undue wear between the rods and the carriage in response to adjusting the vertical position of the carriage relative to the work supporting surface, and such wear can result in a loss of the desired vertical orientation, even if initially obtained, or a worsening thereof if not initially obtained. Still further, the imposition of a load against the router bit during a woodworking operation can impose a load on the router and carriage which, because of the offset relationship between the router axis and support rods further affects the ability to obtain and/or maintain the desired vertical orientation between the router bit axis and work supporting surface during the woodworking operation.
Vibration of the router and router bit during non-loaded operation of the router can result from a lack of precision in machining the component parts of the router support and, even if not present during non-loaded operation, can occur during a woodworking operation as a result of side thrust against the router bit, especially if a support of the router is laterally offset from the axis thereof as in the Darrin apparatus. With further regard to the latter, a lift or adjusting screw by which the carriage and thus the router bit is vertically displaceable relative to the work supporting surface is also laterally offset from the axis of the router and is threadedly interengaged with the carriage for rotation of the screw to displace the latter and the router relative to the work supporting surface. Accordingly, the adjusting screw is also subjected to the imposition of forces resulting from the cantilever support of the carriage and router which promote undue wear between the interengaging threads on the screw and carriage. Ultimately, such wear results in a decrease in the ability to accurately and, or, minutely adjust the position of the carriage and thus the router bit relative to the work supporting surface.
In accordance with the present invention, a support mechanism is provided for a router by which the foregoing and other problems and disadvantages encountered in connection with such mechanisms heretofore provided are advantageously avoided or overcome. More particularly in this respect, a router support in accordance with the present invention advantageously provides for supporting the router and router carriage in balanced suspension beneath the work supporting surface and relative to the router axis and thus the router bit axis. The balanced suspension promotes the ability to obtain and maintain the desired perpendicular orientation between a router bit axis and the work supporting surface, both prior to and during a woodworking operation. Still further, the balanced suspension includes a balanced lift or adjusting screw arrangement by which the carriage and thus the router bit is elevated and lowered relative to the work supporting surface. This advantageously provides for maintaining the desired vertical orientation of the router bit relative to the work supporting surface and promotes the ability to accurately adjust the carriage and thus the router bit height relative to the work supporting surface. Moreover, these advantages are obtained and maintainable throughout the life of the apparatus.
In accordance with one aspect of the invention, the support arrangement includes a pair of support and guide posts for the router carriage on diametrically opposite sides of the router axis, and a pair of lift or adjusting screws on diametrically opposite sides of the latter axis and threadedly interegaging with the carriage for rotation of the screws to displace the latter relative to the work supporting surface. The diametrically opposed relationship between the posts and between the adjusting screws balances the support of the carriage and stabilizes the carriage and thus the router supported thereby relative to the work supporting surface. Thus, the imposition of unbalanced forces on the support mechanism during an adjusting operating and/or during wood working operation is avoided or minimized, thus improving precision of cutting and the ability to repetitively obtain such precision.
In accordance with another aspect of the invention, the lift screws have an end exposed at the work supporting surface and provided with scale plates which can be set relative to a corresponding reference mark on the support surface so as to provide improved accuracy in connection with adjusting the height of a router bit relative to the work supporting surface. In accordance with a further aspect of the invention, the carriage comprises a body portion having an arcuate recess and a clamp plate having an arcuate surface which, together with the arcuate recess, provides an opening for surrounding the housing of a router, thus to firmly support the latter on the carriage with equal radial holding forces about the periphery of the housing. Further, through the use of split collars, the carriage is advantageously adapted to support a number of routers having different housing diameters.
It is accordingly an outstanding object of the present invention to provide an improved support mechanism for supporting a router relative to a work supporting surface in a manner which promotes obtaining and maintaining a desired perpendicular orientation between a router and router bit axis and the work supporting surface.
Another object is the provision of a support mechanism of the foregoing character which promotes stability of the router and router bit against vibration during both loaded and non-loaded operation of the router.
A further object is the provision of a support mechanism of the foregoing character which eliminates or minimizes the imposition of unbalanced forces on the support mechanism.
Yet another object is the provision of a support mechanism of the foregoing character which provides an improved ability to accurately and minutely control adjustment of the position of a router bit relative to the work supporting surface.
Still another object is the provision of a support mechanism of the foregoing character in which the router and router carriage are supported in balanced suspension beneath the work supported surface so as to promote a uniform distribution of forces through the support mechanism during a woodworking operation and a uniform application of forces between the component parts of the support mechanism during use of the router and during adjustment of the position of the carriage relative to the work supporting surface.
Yet another object is the provision of a support mechanism of the foregoing character having an improved carriage structure for supporting routers having different housing diameters.